In general, a circuit board is formed with circuit patterns on an electric insulation substrate with a conductive material such as copper (Cu) and refers to a board prior to mounting of electronic component-related heating elements. Heating elements, such as a semiconductor element, a Light Emitting Diode (LED), and the like, are mounted on the above-mentioned circuit board.
The circuit board on which the LED is mounted is particularly being developed for a head lamp of a vehicle, and thus heat resistance and heat transfer characteristics are required.
However, the elements such as the LED and the like radiate considerable heat. Therefore, if the heat is not dissipated from the circuit board on which the heating elements are mounted, the temperature of the circuit board on which the heating elements are mounted increases, thereby deteriorating product reliability in addition to causing breakdown and malfunction of the heating elements.